Expansion valve

ABSTRACT

A thermal expansion valve for a refrigeration system comprises a working element with a diaphragm clamped between a cover plate and a cover ring. The diaphragm is a multiple-diaphragm comprising two or more individual diaphragms. This makes the multiple-diaphragm more flexible than a single diaphragms and increases the lifetime of the diaphragm. The individual diaphragms are separated by an anti-friction layer to protect against tear, the anti-friction layer can be grease or oil placed between the individual diaphragms or it can be a layer of coating on the diaphragms.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in International Patent Application No. PCT/DK2008/000402 filed on Nov. 12, 2008 and Danish Patent Application No. PA 2007 01606 filed Nov. 13, 2007.

FIELD OF THE INVENTION

This invention relates to a thermal expansion valve for a refrigeration system comprising a working element with a diaphragm chamber. The expansion valve has a closure member which is movable by the force of the working element.

BACKGROUND OF THE INVENTION

A thermal expansion valve usually comprises a working element with a diaphragm clamped between a cover plate and a cover ring. The space above the diaphragm is connected by the way of a capillary tube to a pressure sensor or a pressure-generating temperature sensor, the pressure of which loads the diaphragm from above. The refrigerant pressure prevailing in the valve and a spring bearing against a plate acts on the diaphragm in the opposite direction.

In commercially available thermal expansion valves the diaphragm element is a single diaphragm made of a single layer of metal normally steel. The single diaphragm is exposed to stress and deformation from the forces acting on the diaphragm.

The stress and deformation with time will wear out the diaphragm reducing the life time of the valve.

SUMMARY OF THE INVENTION

The object of this invention is to make a diaphragm element for a thermal expansion valve for a refrigeration system that can stand up to the stress and deformation and improve the lifetime of the diaphragm element.

The problem is solved according to the invention by replacing the normal single diaphragm made of a single layer of metal with a multiple-diaphragm comprising two or more individual diaphragms.

A problem with the multiple-diaphragm is cold welding and wearing between the individual diaphragms. This problem can be solved by adding an antifriction layer between the individual diaphragms. The antifriction layer can be a small amount of grease or oil. Another way to solve this problem is to coat the diaphragms by a layer of carbon, rubber, plastic or a layer of a metal like cobber or tin.

The multiple-diaphragm comprises two or more individual diaphragms, the individual diaphragms in a multiple-diaphragm are thinner than a traditional single diaphragm and therefore the multiple-diaphragm have higher flexibility and are less susceptible to damage due to stress and deformations and therefore the multiple-diaphragm has a longer life time.

This invention is a thermal expansion valve for a refrigeration system comprising a working element comprising a diaphragm chamber, a base ring and a cover plate wherein the diaphragm chamber comprises a multiple-diaphragm placed between the base ring and the cover plate, the multiple-diaphragm comprises two or more individual diaphragms.

The multiple-diaphragm is placed between the base ring and the cover plate, the multiple-diaphragm is made of two, three or more individual diaphragms. The advantage is that the individual diaphragms are thinner than a traditional single diaphragm and therefore more flexible and less affected by stress, strains and deformations and therefore it has a longer life time. The individual diaphragms support each other and therefore the diaphragms element has the same stiffness as a traditional single diaphragm.

Each individual diaphragm is a complete diaphragm and can be used as a single diaphragm. Therefore if one individual diaphragm is broken, for instance by loose metal particles left over from the manufacturing process penetrating the individual diaphragm, then the other individual diaphragms are still in place and the valve is still working.

The individual diaphragms are separated by an antifriction layer. This is because without an antifriction layer the individual steel diaphragms can glide against each other and the friction causes tear and cold welding destroying the individual diaphragms. To avoid this, a layer of antifriction material is placed between the individual diaphragms.

The antifriction layer can be grease or oil or another suitable fluid. This solves the problem avoiding friction between the individual diaphragms.

The antifriction layer can also be rubber or plastic. This could be a layer of double adhesive tape. This is easier in the assembly process to place a slice of rubber or tape between the individual diaphragms than to use grease or oil.

Instead of placing a layer of grease, oil or some other material between the individual diaphragms, the diaphragms can be coated by a suitable material. This makes the assembly process even easier since no extra material is added during the assembly process.

The coating can be made of carbon, rubber or a plastic material. For instance diamond like carbon or Teflon can be used. The coating can also be made of cobber, tin, zinc, silver, nickel or another suitable metal or alloy. Besides protecting against tear and cold welding coating also makes the diaphragm harder and less likely to be damaged in case there should be loose metal particles in the valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in further detail hereinafter with reference to a preferred embodiment illustrated in the drawings, in which

FIG. 1 shows a valve according to this invention.

FIG. 2 shows the working element according to this invention.

FIG. 3 shows an exploded view of the working element in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the embodiment described the multiple-diaphragm comprises two individual diaphragms. But according to this invention the multiple-diagram can also comprise three or more diaphragms.

The valve 1 shown in FIG. 1 is an expansion valve for a refrigeration system. It comprises a housing 2 with three nozzles, namely a nozzle 3 for the incoming liquid coolant, a nozzle 4 for the outgoing coolant, a nozzle 5 for connection to a sensor line and a spindle 6. One end of the housing 2 is closed by a working element 9; the working element comprises the base ring 10, the diaphragm chamber 11 and a cover plate 12. The diaphragm chamber is connected by way of a capillary tube 13 to a sensor 14.

FIG. 2 shows the working element 9 with the base ring 10, diaphragm chamber 11, a cover plate 12 with a connecting passage 13 a for connecting the capillary tube (not shown), a plate 18, a bolt 19 and the multiple-diaphragm 15. In this embodiment the multiple-diaphragm comprises two individual diaphragms.

The double diaphragm 15 is therefore pressurised from above by the pressure owing to evaporation of the fluid in the sensor 14 and is pressured from below by the pressure of the refrigerant, which is detected at the nozzle 5, and by a spring, not illustrated.

FIG. 3 shows an exploded view of the working element 9 with the base ring 10, a cover plate 12, a plate 18, a bolt 19 and the multiple-diaphragm comprising in this embodiment a first diaphragm 16 and a second diaphragm 17.

A diaphragm is typically made of stainless steel. The individual diaphragms in the multiple-diaphragm typically are 0.08-0.20 mm thick. The multiple-diaphragm with two 0.08 mm thick individual diaphragms has the same stiffness as a 0.1 mm thick single diaphragm.

In the above embodiment two identical individual diaphragms is used. However it is also possible to use two or more diaphragms that are slightly different and fit better together. This could be done by forming the individual diaphragms at the same time using the same tool, so the waves in the individual diaphragms fit exactly. This will reduce the forces acting between the individual diaphragms and reduce the risk of tear. 

1-7. (canceled)
 8. A thermal expansion valve for a refrigeration system comprising a working element comprising a diaphragm chamber, a base ring and a cover plate wherein the diaphragm chamber comprises a multiple-diaphragm placed between the base ring and the cover plate, the multiple-diaphragm comprises two or more individual diaphragms and the individual diaphragms are separated by an antifriction layer.
 9. The thermal expansion valve according to claim 8 wherein the antifriction layer is grease or oil or another suitable fluid.
 10. The thermal expansion valve according to claim 8 wherein the antifriction layer is rubber or plastic.
 11. The thermal expansion valve according to claim 8 wherein the individual diaphragms comprises a coating.
 12. The thermal expansion valve according to claim 11 wherein the coating is made of carbon, rubber, Teflon or a plastic material.
 13. The thermal expansion valve according to claim 11 wherein the coating is made of cobber, tin, zinc or another suitable metal or alloy. 